core: run many bricks within one glusterfsd process

This patch adds support for multiple brick translator stacks running in
a single brick server process.  This reduces our per-brick memory usage
by approximately 3x, and our appetite for TCP ports even more.  It also
creates potential to avoid process/thread thrashing, and to improve QoS
by scheduling more carefully across the bricks, but realizing that
potential will require further work.

Multiplexing is controlled by the "cluster.brick-multiplex" global
option.  By default it's off, and bricks are started in separate
processes as before.  If multiplexing is enabled, then *compatible*
bricks (mostly those with the same transport options) will be started in
the same process.

Backport of:
> Change-Id: I45059454e51d6f4cbb29a4953359c09a408695cb
> BUG: 1385758
> Reviewed-on: https://review.gluster.org/14763

Change-Id: I4bce9080f6c93d50171823298fdf920258317ee8
BUG: 1418091
Signed-off-by: Jeff Darcy <jdarcy@redhat.com>
Reviewed-on: https://review.gluster.org/16496
Smoke: Gluster Build System <jenkins@build.gluster.org>
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
Reviewed-by: Shyamsundar Ranganathan <srangana@redhat.com>

1 files changed, 13 insertions, 2 deletions

diff --git a/libglusterfs/src/common-utils.c b/libglusterfs/src/common-utils.c
index 18c2a39d60e..bcf9d9d7b90 100644
--- a/libglusterfs/src/common-utils.c
+++ b/libglusterfs/src/common-utils.c
@@ -3646,15 +3646,17 @@ gf_is_service_running (char *pidfile, int *pid)
         int             fno = 0;
 
         file = fopen (pidfile, "r+");
-        if (!file)
+        if (!file) {
                 goto out;
+        }
 
         fno = fileno (file);
         ret = lockf (fno, F_TEST, 0);
         if (ret == -1)
                 running = _gf_true;
-        if (!pid)
+        if (!pid) {
                 goto out;
+        }
 
         ret = fscanf (file, "%d", pid);
         if (ret <= 0) {
@@ -3663,6 +3665,15 @@ gf_is_service_running (char *pidfile, int *pid)
                 *pid = -1;
         }
 
+        if (!*pid) {
+                /*
+                 * PID 0 means we've started the process, but it hasn't gotten
+                 * far enough to put in a real PID yet.  More details are in
+                 * glusterd_brick_start.
+                 */
+                running = _gf_true;
+        }
+
 out:
         if (file)
                 fclose (file);